The present invention relates generally to three-phase active rectifiers, and in particular to a hybrid planar common-mode choke utilized in conjunction with active rectifiers.
A switching-mode power conversion system that includes an active rectifier and a motor drive inverter generates high frequency (HF) voltage components that cause HF leakage currents and conducted electromagnetic interference (EMI), or “noise.” This noise flows within power-feeding paths, and between the power conversion system and ground. The resulting HF currents are classified in common-mode (CM) and differential-mode (DM) components according to their circulation paths. Modern power conversion systems must meet strict EMI requirements, so filtering of electromagnetic noise is a significant concern.
Three-phase active rectifiers are utilized to meet strict input current harmonics requirements during power conversion of a three-phase alternating current (AC) input into a direct current (DC) output. Leakage current generated by a CM voltage of the active rectifier is the primary concern related to conducted and radiated EMI. Due to the HF leakage current conducted from the active rectifier through the earth ground, the CM current circulation loop is relatively large compared to that of the DM current. The large circulation loop acts as an antenna for the radiated EMI. A filter is often employed to handle this generated CM electromagnetic noise. Prior art filters have been designed utilizing, for example, chokes that are implemented in a stacked configuration that include several toroidal cores stacked upon one another to achieve a desired CM inductance. This configuration, however, is difficult to accommodate in power converters that are subject to significant shock and vibrations. It is desirable to eliminate/reduce stacking of CM choke inductor cores to eliminate/reduce stresses created in high shock and vibration environments.